Both behavioral and averaged evoked potential (AEP) responses during the perception of auditory patterns will be studied in normal adult subjects with the goal of defining the underlying psychophysiological mechanisms. Stimulus patterns will be three temporally spaced tone or noise bursts involving two frequencies ("high" and "low") or two intensities ("loud" and "soft"). The finding that normal subjects often reverse acoustic cues in auditory pattern discrimination will be used as an investigative tool in the AEP part of the project. Spectral analyses of the EEG and early and late components of the AEP's associated with three classes of responses (accurate, reversed, and non-reversal errors) to the same stimulus patterns will be studied to determine whether any of the pre- or post- stimulus electrophysiological correlates of the stimulus-response relationship permit prediction of response accuracy prior to complete presentation of the pattern. Behavioral studies of auditory pattern perception will document its development in normal young children. Then, it will be related to delayed language development and learning disabilities in groups of children with these disorders. Performance of patients with hemispheric lesions should contribute further information about the cerebral mechanisms involved in auditory pattern perception so that useful diagnostic procedures may be developed.